Deep groove ball bearings are most commonly used rolling bearings. Because of their versatility, single-row deep-groove ball bearings are the most popular of the antifriction bearing types. They are available in a broad range of sizes, from miniature ball bearings with outside diameter of less than 9mm to extra-large bearings that exceed 1, 500mm in diameter. Small and mid. size bearings are also available in a variety of shield, seal and snap ring arrangements. Big ones normally are fitted with solid brass or steel cages.